I'm trying to make a custom module which requires a boolean field to be added in the contact window.

To be more specific, in the "Sales" tab under the menu "Customers", then you select a customer and then under the tab "Contacts". When you select a contact a window opens where it shows you some information about the contact. I would like to add a boolean field there.

So there's a python file in the custom module where I've added the column: